CSLB C-36 Plumbing ContractorRough-in PlumbingMedium
A plumbing contractor is installing a new residential gas piping system. The gas meter is located on the exterior of the building. The piping from the meter to the first appliance shut-off valve is 1-inch Schedule 40 black steel pipe. What is the maximum allowable unsupported horizontal length for this 1-inch pipe, according to the California Plumbing Code (CPC)?
- A10 feet
- B12 feet
- C8 feet
- D15 feet
Show answer & explanationAnswer & explanation
Correct answer: A. 10 feet
The California Plumbing Code specifies maximum unsupported lengths for gas piping to prevent sagging and stress on joints. For 1-inch Schedule 40 black steel pipe, the maximum allowable unsupported horizontal length is 10 feet.
Why the other options are wrong
- B. 12 feet is the limit for 1 1/4-inch pipe, not 1-inch.
- C. 8 feet is the limit for 3/4-inch pipe, not 1-inch.
- D. 15 feet is the limit for 1 1/2-inch pipe, not 1-inch.
Gas Pipe Unsupported Length (Horizontal)
The maximum distance a horizontal gas pipe can extend between hangers or supports without sagging or placing undue stress on connections.
- Prevents pipe damage and leaks.
- Varies by pipe material, size, and orientation.
- Specified in the California Plumbing Code (CPC).
Memory trick: Gas Pipes Get Good Support.